1. Field of the Invention
The present invention relates to a method of continuously forming a pair of top end stops, or a separable bottom end stop composed of a separable pin and a box pin, molded integrally on a continuous slide fastener chain at each of successive element-free spaces formed in the slide fastener chain at longitudinal intervals, and a chain splitting apparatus suitable for use in the end-stop forming method.
2. Description of the Prior Art
It has been customary to continuously attach various types of end stops, such as top end stops, bottom end stops, and separable bottom end stops composed of separable pins and box pins, by an end-stop attaching apparatus to a continuous slide fastener chain (hereinafter referred to, for brevity, as "chain") at ends of element-free space portions formed in the chain at longitudinal intervals. In this instance if the end stops are of the type which are composed, such as top end stops or separable bottom end stops, of a pair of end stop members to be attached to inner longitudinal edges of a pair of fastener tapes (hereinafter referred to, for brevity, as "tapes"), there is a need to spread open each of the element-free portions so that the two end stop members can be readily inserted in the element-free space portion and subsequently attached to the inner longitudinal edges of the tapes.
For a purpose of spreading the element-free space portions, two typical methods have been used as disclosed, for example, in Japanese Utility Model Laid-open Publication No. 62-42410 and Japanese Patent Publication No. 1-28564, respectively. The first spreading method employs a chain splitting member which is inserted into an element-free space portion of a chain so as to disengage some interengaged coupling elements progressively from opposite ends of the element-free portion. In the second spreading method, two parallel spaced stringers jointly forming a chain and having successive spaced rows of disengaged coupling elements are fed simultaneously while they are properly positioned for the attachment of the end stop members.
In a continuous slide-fastener manufacturing system, the chain is passed through various processes, such as finishing of woven tapes, attachment of coupling elements, and application of reinforcing films before it is introduced into the end-stop attaching process. During that time, since the chain is repeatedly tensioned and slackened, difficulties would arise in maintaining the desired dimensional accuracy of the two tapes throughout the processes. According to a conventional practice, the portions to be processed are positioned at each procces to maintain the dimensional accuracy. However, it still retains the possibility that a dimensional difference created between the two tapes is increased during a prolonged continuous run of the manufacturing system. Especially, in the case of the end-stop attaching process in which the interengaged rows of coupling elements are partly disengaged to forcibly spread open the tapes as in the first spreading method described above, it occurs likely that when the disengaged rows of coupling elements located next to the element-free space portion are reengaged in a subsequent process, the dimensional accuracy between the two tapes is lowered or deteriorated, thereby causing various problems.
In the end-stop attaching process in which the aforesaid second spreading method is used, the opposed, fully disengaged rows of coupling elements are engaged together throughout the length thereof after the attachment of the end stop members is completed. In this instance, however, since a dimensional difference between the two tapes tends to be increasingly large in the preceding processes, a position of engagement between the opposed rows of coupling elements is liable to deviate from a desired point.